It is believed to be understood to lead electrical contactings through a wafer or a partial area of a wafer. This type of contacting is used, for example, in the case of components which are intended for flip-chip mounting. However, vias also permit three-dimensional packaging designs, where several components are superposed vertically and contacted. Therefore, vias are gaining increasing importance.
In the European Patent Application EP 1 671 924 A2, a micromechanical sensor element of the type indicated at the outset is discussed, whose micromechanical structural elements are realized in a functional layer of the layer construction. They are engaging interdigital structures having fixed and deflectable electrodes. For the electrical connection of these electrodes, conductor tracks are integrated into the layer construction between the substrate and the patterned functional layer. These conductor tracks are each in direct contact with a substrate connection area forming a via. Each connection area is completely surrounded by trenches which were produced in the substrate by a back-side trenching process after completion of the layer construction, and extend over the entire thickness of the substrate. These trenches form an insulating frame which electrically insulates the connection area from the adjoining substrate. The insulating frame of the vias discussed in EP 1 671 924 A2 is filled superficially at best, and specifically, with the material of an insulating layer which is applied on the back side of the substrate and patterned after the back-side trenching process and prior to a metallization, so that the metallization is connected with the connection area.
In practice, this realization form of a via proves to be problematic in two respects. First of all, the insulating properties of open trenches are indefinite. For example, these properties may be impaired by contamination during the manufacturing or dicing process or perhaps at the location the component is used, so that the electrical reliability of the via suffers. Secondly, the mechanical stability of vias having an open insulating frame is essentially a function of its geometry, i.e., its form, depth and width. However, the mechanical stability of a via must always satisfy the same minimum requirements for an external contacting by wire bonding, for example.